Conventionally, an interconnection pattern used in an LSI package is generally formed by a plating method using photography. According to this method, a copper thin film that serves as a base of an interconnection pattern is formed on insulating resin by a sputtering method or the like. Photosensitive resin for forming etching resist is coated by using a spin coater or the like. Thereafter, for purposes of forming the etching resist, a pattern formed portion is exposed and developed by using a photo-mask so that the resin of a portion other than the developed portion is removed. By removing copper film other than a section of the interconnection pattern by etching, the interconnection pattern is completed. In order to protect the copper interconnection pattern, a solder resist is formed on all portions other than external electrode pads. The plating of material such as Ni, Ni/Au, and Ni/Pd/Au is performed to form a barrier layer for suppressing diffusion of copper into a solder supplied onto the external electrode pads, thus completing the interconnection pattern used in the LSI package.
On the other hand, an attempt is recently made to form the interconnection pattern by a printing and coating method of conductive resin or conductive ink in place of the above-mentioned interconnection pattern using a so-called photolithographic method. According to the method using the conductive resin, if the interconnection pattern is formed by a screen printing method and the resin is then hardened, circuit interconnections can be quickly produced and manufacturing steps can be considerably shortened. Further, because of an additive structure, this is an environmental friendly technique according to which removed components such as copper and waste fluid such as etchant are not produced.
Conventional techniques discovered by an applicant of the present application by a search are as follows:
First conventional example: Japanese Patent Application Publication (JP-P2006-13248A)
Second conventional example: Japanese Patent Application Publication (JP-P2006-253175A)
Third conventional example: PCT international Publication WO2004/038793.